As is well known, condensation boilers are a particular kind of heat generators, which are designed for cooling the combustion products down to a temperature below the dew point of the burnt gas, so that the partial condensation of water formed in the combustion reaction is obtained, said water usually leaving the boiler itself in the form of overheated steam.
According to the rules in force at present, gas-fired boilers whose power is lower than 30,000 kcal/hr can also installed in residential buildings.
In that case, the pipe for discharging smokes is connected to the flue and, as an alternative, to the outside with a short connecting pipe through an outer wall.
The condensate is then expelled through the sewer system of the house itself.
In order to prevent the possible egress of discharge gases through the condensate drainage conduit, the conduit itself is conventionally configured as a "drain-trap" so as to create, with the liquid that forms and accumulates within such trap, a hydraulic seal of the conduit that allows the condensate to be drained, which prevents the toxic discharge gases from passing, so that they cannot flow into the various rooms through the sewer system.
It has been observed that sometimes working conditions can occur in such systems, in which no condensate forms or in which the condensate, though formed at first during the starting step, can progressively evaporate.
Among such conditions one could mention, for instance, the case in which a condensation boiler in installed in a conventional heating plant designed for operating at a return temperature higher than the dew point temperature.
Under such condition, an amount of water sufficient to fill the drain trap is unlikely to form, so that there is insufficient water for hydraulically closing said condensate drain trap.
Such condition is a source of possible danger, owing to the fact that burnt gases may be conveyed so as to leave the pressurized combustion chamber partially through the condensate drainage connecting pipe so that they flow into inhabited rooms.
Accordingly, it is evident that there is a need for a further safety device that operates as a burnt gas interceptor and that prevents the burnt gases from flowing into the inhabited rooms when the hydraulic drain-trap does not form.